In general, when an engine is operated, air and fuel are supplied to a combustion chamber of a cylinder. The fuel is injected by an injector, whereas the air is supplied to the combustion chamber by the operation of a cam and a valve provided in a cylinder head. In such a case, it is necessary to adjust the switching time or opening degree of the valve according to the operating range of the engine. In order to transfer the intake air in the cam and the valve to the combustion chamber in the related art, the valve arranged on the upper surface of the combustion chamber is opened and closed through the cam using a hydraulic circuit.
FIG. 1 is a view illustrating a conventional valve switching apparatus. In the conventional valve switching apparatus, the switching time and opening degree of a vale 10 are controlled through a cam 20 using a hydraulic circuit. The hydraulic circuit consists of a plurality of components such as a pump unit 30, a high-pressure chamber 40, an accumulator 50, a deaerator 60, an intermediate-pressure chamber 70, a check valve 80, a solenoid valve 90, and a brake unit 95. For this reason, the hydraulic circuit has disadvantages of having a complicated structure and increased weight and costs. In addition, since a response of the hydraulic system is delayed when the volume of the closed circuit is increased, the performance of the hydraulic system is decreased
Accordingly, there is a need for a valve switching apparatus having a simple structure and an improved response while controlling the switching time and opening degree of a valve through a cam.
The matters described as the related art have been provided only for assisting the understanding for the background of the present disclosure and should not be considered as corresponding to the related art already known to those skilled in the art.